CEPC 650MHz Klystron R&DZusheng ZHOU

On behalf of High Efficiency RF Source R&D CollaborationInstitute of High Energy Physics

Jan. 21, 2020

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Outline1st prototype tube• Manufacture completed

• Conditioning progress

High efficiency design• High voltage klystron

• Multi-beam klystron

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1st prototype tube

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1st prototype tubeConventional method based on 2nd harmonic cavity in order toinvestigate the design and manufacture technologies for highpower CW klystron.

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Main parameters GoalFreq. (MHz) 650Vk (kV) -81.5Ik (A) 15.1Perveance (µP) 0.65Efficiency (%) >60Output power (kW) 8001dB bandwidth (MHz) ±0.5

Design Parameters

Mechanical design

Components manufacture

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Modulator anode Input coupler Cooling pipe Gun welding edge

Cavity body Cavity nose Coil Collector

Gun subassembly

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Focusing electrode and support assembly Modulator anode assembly

Cavity and window components

74th CAV Window

Input coupler loop 1st CAV 2nd CAV 3rd CAV

5th & 6th CAV

Cavity brazing and cold test

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Cavity brazing Cold test

The measured frequency is within design scope.

Parameters 1st 2nd 3rd 4th 5th 6th

Frequency（MHz）Design 650.5 649.5 1293.5 669.2 668 649.5

Measure 650.2 649.29 1293.1 668.98 668.68 649.15

QeDesign 291.4 67

Measure 292.2 69.4

Leak test

Collector brazing

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Collector brazing

Gun processing

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Temperature measurement Gun processing

Auxiliary components

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Girder

Coil

Oil tank

There is about 3% error between the measurement results and the simulation values. Theexcitation current of the solenoids will be adjusted to meet the design requirements.

Coil measurement

Vacuum-Assy assembly

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Component leak test

Cavity assemble

Collector assemble Final welding Completed assembly

Final assemble is completedon Oct.19

Prototype bake-out

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Prototype installation Top view

Bake out is started from Oct.26 and finished on Nov.24.

Prototype bake-out

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Tube temperature(430°C)

Filament current(30A)

Vessel pressure(-6Pa)

Tube Pressure(-8Pa)

Almost one month

Final assembly

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Klystron pinch off Lead shield

Vertical to horizontal

Horizontal placement

Coil installation

Remove assembly bracket Final placement on Dec. 11

Water jacket installation

Packing and Transportation

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Before delivery Packing

Leave factory on Dec.24(10:30)

Loading

Arrived IHEP on Dec.25(21:00)

Unloading and In place

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Unboxing and unloading

In place at 2nd floor of building 1 on Dec. 26

Lifting

Test condition preparationHigh voltage power supply: ADS projectHigh power load: ADS project (400kW max.)

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Interlock and data collectionWater cooling and waveguide system connectionLLRF and arc detector

High voltage conditioning is started from this year.

Test procedure

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① Cathode Low-voltage emission test② Vacuum treatment and cold voltage conditioning③ High voltage conditioning④ RF processing⑤ Power and stability

Test condition preparation

Until Jan.19

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① Cathode Low-voltage emission test-FINISHED② Vacuum treatment and cold voltage conditioning-FINISHED③ High voltage conditioning-UNDERWAY④ RF processing⑤ Power and stability

Conditioning status

High efficiency design

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High efficiency designGOAL Scheme 1：With high voltage gun (110kV~120kV/9.1 A), low perveanceScheme 2：MBK, 54 kV/20A electron gun

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Parameter Scheme1 Scheme2Freq. (MHz) 650 650Voltage (kV) 110 54Current (A) 9.1 20(2.5×8)Beam No. 1 8Perveance (µP) 0.25 1.6(0.2×8)Efficiency (%) ~80 >80Power(kW) 800 800(100×8)

High voltage klystron

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High efficiency design

AJDISK(1D) EFF: 85.6% KLYC(1D) EFF: 85.6% EMSYS(2.5D) EFF: 81.4%

CST(3D) EFF(asymmetrical output): 78.2%

The 110kV design is almost finished and 3Defficiency is up to 78.2%. 120kV design ison going and expect higher efficiency.

Multi-beam klystron Parameters Unit ValueGun Voltage kV 54

Beam number 8

Beam perveance μP 0.2

Output power kW 875

Gain dB 44.2

Efficiency(3-D simulation) % 80.7

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MBK Length

Component Unit Value

RF interaction m 1.9

Gun m 0.5

Collector m 1.0

Total m 3.4

3-D PIC simulation predicts bandwidth of ±0.8 MHz

MBK bandwidth curve by CST20

Multi-beam klystron

Gun design

5MV/m

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Multi-beam klystron

Parameters Unit Value

High voltage kV 54

Current A 8*2.5

Beam waist mm 7.5

Filling ratio 0.625

Electric filed on cavities

MBK output window design

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Multi-beam klystron

The output window design is almost completed

Design progress status

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Multi-beam klystron

Design title Status

MBK beam dynamicsGoal 1 : output power> 800kW Goal 2 :efficiency >80%

Finished Finished

Design on input and output cavity Finished

Gun design Finished

Design on output window Finished

Coil design In progress

MBK collector In progress

We are fully prepared for future possibility of manufacture.

Summary• The components machining, brazing, welding and final assembly for

1st prototype are finished in collaboration partner.

• The conditioning and commissioning of 1st prototype is started at thebeginning of this year.

• The both schemes for high efficiency design are progressing well.

• The mechanical design for 2nd tube(high efficiency) will be start aftercompletion of design review.

• The design of MBK is fully prepared for next stage.

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Thanks for your attention!